In the fabrication of semiconductor devices, wafers of semiconducting nature, such as silicon wafers, must be processed through a multiplicity of fabrication steps which can amount to several hundred steps for a complicated IC device. For instance, a wafer is normally processed through a variety of fabrication steps which may include oxidation, dielectric layer deposition, stress relief and annealing, ion implantation, planarization, chemical-mechanical-polishing, etc. In each of these processing steps, the wafers are processed either singularly or in batches by loading them into a process machine or a wafer boat that can hold up to 24 wafers and then processing them in a horizontal or in a vertical processing chamber. The wafers can also be processed singularly in fabrication chambers that only process one wafer at a time. In-between the processes, the wafers are stored in a wafer storage cassette. One of such popularly used cassettes can hold up to 24 wafers vertically positioned in the cassette. The wafer must be picked-up by a suitable tool for loading or unloading into or from a wafer storage cassette to either a wafer boat or a process chamber for processing a single wafer, or for transferring between process tools.
Wafer pick-up tools of various configurations have been designed and utilized for handling wafers in a semiconductor fabrication facility. Since wafers are processed in a clean room environment and cannot tolerate the presence of any contaminants, a wafer pick-up tool must be designed to satisfy this important requirement. It is expected that most mechanical pick-up devices, e.g., a clamping device, would generate contaminants due to its mechanical contact with a wafer surface. Consequently, a pick-up device that utilizes vacuum for contacting and holding the wafer is more desirable. Most commercially available vacuum pick-up devices consist of a handle and a fixed-position pick-up head.
A vacuum pick-up device may also be used for wafers in-between process stations in an electrochemical plating process. In such a process, a wafer must be transferred in-between acid and alkali tanks for conducting various plating steps. During the various plating steps, the surface of the wafer is frequently contaminated with particles or acid/alkali solutions which may greatly affect the efficiency of the vacuum pick-up process. It is therefore desirable to provide a vacuum pick-up tool for wafers that not only can pick up wafers, but also is can detect the status of the vacuum used for the pick-up and alert the operator of any possible failure. The vacuum pick-up device can also detect when a wafer is stuck on the pick-up device due to adhesion of contaminating liquids on the surface of the pick-up device.
It is therefore an object of the present invention to provide an automatic sensing wafer blade for picking up wafers that does not have the drawbacks or shortcomings of the conventional wafer pick-up blades.
It is another object of the present invention to provide an automatic sensing wafer blade for picking up wafers that is capable of indicating a status of the vacuum pick-up process.
It is a further object of the present invention to provide an automatic sensing wafer blade for picking up wafers that is capable of predicting a potential failure of a seal ring on the pick-up blade.
It is another further object of the present invention to provide an automatic sensing wafer blade for picking up wafers that is capable of detecting contaminating particles on the surface of the pick-up blade.
It is still another object of the present invention to provide an automatic sensing wafer blade for picking up wafers that is capable of detecting contaminating liquids on the surface of the pick-up blade.
It is yet another object of the present invention to provide an automatic sensing wafer blade for picking up wafers that is equipped with at least one sensor of a limit switch.
It is still another further object of the present invention to provide an automatic sensing wafer blade for picking up wafers that is equipped with at least one sensor that is a capacitance sensor.
It is yet another further object of the present invention to provide an automatic sensing wafer blade for picking up wafers that is equipped with a V-shaped seal ring on the surface of the pick-up blade for functioning as a vacuum seal.